Firefighters, emergency response personnel, members of the military, racing personnel, and industrial workers that can be exposed to flames, high temperatures, and/or electrical arcs and the like, need protective clothing and articles made from thermally resistant fabrics. Any increase in the effectiveness of these protective articles, or any increase in the comfort or durability of these articles while maintaining protection performance, is welcomed.
Rigid-rod para-aramid and polyazole fiber has good low thermal shrinkage when exposed to high heat flux or flame and therefore is desired for protective apparel. Unfortunately, such rigid-rod fibers fibrillate easily upon abrasion. Their highly-ordered rigid-rod structure has a propensity for fibrillation attributable to the lack of lateral forces between macromolecules. As the content of such fibers in a fabric increases above 5 weight percent, the extent of potential fibrillation of the fibers also increases and actual fibril formation can become more noticeable and objectionable. Therefore what is desired is to reduce the fibrillation of fabrics and apparel containing such rigid rod fibers without adversely affecting the ability of the protective apparel to protect the wearer.
A fiber known as polysulfonamide fiber (PSA) is made from a poly (sulfone-amide) polymer and has good thermal resistance due to its aromatic content and also has low modulus, which imparts more flexibility (i.e. comfort) to fabrics made from the fiber; however, the fiber has low tensile break strength. This low tensile strength in fibers has a major impact on the mechanical properties of fabrics made from these fibers. PSA, however, does not readily fibrillate so there is a desire to utilize this comfortable fiber in protective apparel that can be affected by abrasive environments, especially in applications such as firefighters' turnout coats that must function in extreme environments.